feat(lotus): io.lotus.set_deafen action — deafen remote audio at the source

New toWidget action { deafened, screenshareAudioMuted } that sets each remote
RemoteParticipant.setVolume per source (Microphone + ScreenShareAudio), applied
to existing participants + re-applied to late joiners via
RoomEvent.ParticipantConnected (subscribed through vm.livekitRoomItems$). Closure-
scoped state, matching the sibling lotus modules; the cinny host re-sends on join
so a fresh call never inherits stale deafen state.

Replaces cinny's brittle iframe-DOM <audio>.muted hack (which broke on EC
re-render / late tracks). Folded into unpublished 0.20.1-lotus.2.

Note: injected/soundboard audio (Track.Source.Unknown) is not silenced — the
livekit-client setVolume type only accepts Microphone|ScreenShareAudio.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lotus/lotusActions.ts

@@ -29,6 +29,8 @@ export enum LotusWidgetActions {
   SetQuality = "io.lotus.set_quality",
   /** toWidget: per-user avatar-decoration image URLs for in-call tiles. */
   Decorations = "io.lotus.decorations",
+  /** toWidget: deafen remote audio (and optionally mute screenshare audio). */
+  SetDeafen = "io.lotus.set_deafen",
 }
 
 /** toWidget Lotus actions that must be allow-listed in `initializeWidget`. */
@@ -37,4 +39,5 @@ export const LOTUS_TO_WIDGET_ACTIONS: LotusWidgetActions[] = [
   LotusWidgetActions.InjectAudio,
   LotusWidgetActions.SetQuality,
   LotusWidgetActions.Decorations,
+  LotusWidgetActions.SetDeafen,
 ];